The strain of E. coli linked to McDonald’s Quarter Pounders is one of the leading causes of foodborne illness in the U.S.

On Oct. 22, the Centers for Disease Control and Prevention announced that an outbreak of the bacterial infection had sickened at least 49 people in 10 states. One person has died.

While there are many types of harmless E. coli, there are six that can cause diarrhea , including O157:H7, which may have contaminated raw onions used on the burgers, according to federal health officials. Here’s what to know about staying safe from E.

coli. What is E. coli? Escherichia coli is a type of bacteria that spreads in feces and can contaminate food, potentially causing serious infection.

Shiga toxin-producing E. coli (STEC) is the most common type in high-income countries, like the U.S.

It's the type of E. coli that has been implicated in the McDonald’s outbreak. Although STEC infection most severely affects children younger than 5 years old and adults aged 65 and older, anyone can be infected.

“This one is the dying kind,” said Prashant Singh, a food safety microbiologist at Florida State University, stressing the danger of this type of E. coli. According to the CDC , symptoms commonly include bloody diarrhea, severe stomach cramps and vomiting.

In vulnerable groups, E. coli infection can also lead to serious kidney complications and death. People can become infected after consuming contaminated food or water, or coming into contact with the feces of animals.